This invention relates to a telescope mirror assembly which has a deformable glass-ceramic mirror body, support elements engaging the mirror body and setting drives which are mounted on a supporting space frame and by means of which the supporting elements are adjustable in their position relative the space frame to thus displace defined areas of the mirror body.
One of the greatest challenges of modern astronomy is the detection of celestial bodies of extremely weak light, which are situated at a distance of many billions of light years from earth. To make possible such a detection, an enlargement of the light-gathering surface of the telescope mirrors is required while the surface accuracies are preserved or even augmented in the nanometer range.
In the periodical "Journal of Modern Optics" 1987, Volume 34, No. 4, on pages 485-509 the proposal has been submitted to so design a telescope mirror that it is deformable by means of drive mechanisms mounted on a supporting structure for improving the optical quality and economy of large telescopes. According to the proposal the mirror body merely lies, by virtue of its large own weight, on the respective supporting elements so that a deformation in the direction of the supporting structure is effected exclusively by gravity, taken up by an expensive setting mechanism.
In the "Technische Mitteilung Krupp" ("Krupp Technical Bulletin"), Volume 1 of 1990, pages 27-42, a telescope is described which has a mirror body supported by a space frame formed of node elements of Invar steel interconnected by space frame struts. The struts include pipes made of carbon fiber reinforced plastic on which coupling cones also made of Invar steel (Ni 36) are secured by an adhesive.
An optical surface adapted for a telescope is obtained if the root mean square (rms) of the surface errors does not exceed a value in the magnitude of rms=.lambda./28 wherein .lambda. is the wavelength of light. In case of visible light, care has to be taken that the mirror surface has, under all operating conditions, an rms value of less than 18 nanometer.